1. Field of the Invention
The present invention relates generally to methods and systems providing telephony communications through packet-switched communication networks. Particular aspects of the invention relate to location-based services in Internet Protocol (IP) based packet switched mobile communication networks, a method of making location-based services available to network subscribers when roaming between or within such communication networks, and the support and routing of emergency calls in such communication networks.
2. Discussion of the Related Art
Communications services have historically been provided over circuit-switched networks such as the Public Switched Telephone Network (PSTN), but now they can also be provided over packet switched networks, such as the Internet. These packet-switched networks are commonly referred to as IP networks because the Internet Protocol is the most commonly used primary protocol. Many modem wireless networks utilize a combination of telephony equipment (such as conventional cellular phones) and packet switched equipment (usually network traffic routing equipment) compliant with one or more IP telephony standards such as, for example, the International Telecommunications Union (ITU) H.323 standard or the Internet Engineering Task Force (IETF) Session Initiation Protocol (SIP) specification, RFC 2543.
There have been several proposals for a new 3rd generation of IP based mobile networks in which the user equipment (UE) as well as the network equipment (NE) is compliant with one or more IP standards for packet switched networks. However, when providing voice call services, such Mobile IP Telephony (MIPT) networks have several problems which are not present in conventional 2nd generation cellular networks. For example, while cellular subscribers can often roam between 2nd generation cellular networks, it is difficult for IP Telephony (IPT) subscribers of MIPT networks to easily access the same services available in their home network when they are visiting in other networks.
There is, for example, the Mobile IP Protocol to enable mobility. As an example, it is possible that an IPT subscriber, with General Packet Radio Service (GPRS) access in the visited network (see 3G TS 23.060, Stage 2, version 3.3.0), uses voice call services in their home network, so the subscriber is registered in a call control entity (such as a call state control function (CSCF)) in the home network. However, for certain services, such as emergency 911 calls, it is necessary to use voice call services in the visited network and to provide location-based services for successful implementation. Therefore, there is a need for a technique that allows roaming IPT subscribers to easily access and utilize location-based services, and to make emergency calls, in MIPT networks.
In particular, when an emergency call setup request is received by a call control entity in a 2nd generation cellular network, it selects a Public Safety Access Point (PSAP) to route the call to based on the Cell ID or the location information provided during the call setup. However, this method cannot always be performed in 3rd generation mobile IP networks based on the UMTS standard, since the Cell ID or location information may not always be available to a call control entity due to the way the emergency calls are setup. Therefore, there needs to be a method to support the selection of the PSAP in 3rd generation mobile IP networks based on the UMTS standard.